The Southern California Edison energy company contracted out Tesla last week to provide 20-megawatts of energy storage equipment to their power grid. The equipment will be used to stop blackouts should the grid’s main fossil-fuel based energy sources fail. The Tesla Powerpack energy storage units will be installed at a SCE substation in Mira Loma and must be up and running by the end of December.

The amount of equipment being installed is enough to keep 2,500 homes with power for a day, or enoughto charge 1,000 Tesla cars, the company claimed in a blog post.

The cost of the complete energy storage system isn’t clear. As noted by Bloomberg, a 2-megawatt Tesla energy storage system runs around $2.9 million, and contracts that involve more energy than that are negotiated on a per-situation basis.

In late 2015, the Aliso Canyon natural gas reservoir ruptured, causing a major spill of methane gas and forcing over 8,000 local residents out of their homes. Following this incident, the California government has been attempting to expand its energy-storage storage efforts to prevent any potential loss of power during times of high electricity usage.

Last month, California officials green-lighted two other grid energy-storage contracts that would account for 37-megawatts of storage.

This project is one of the most notable happenings on the energy side of Tesla since the company set out to buy SolarCity in August.